Opportunities and constraints for medium-scale organic waste treatment with fly larvae composting.

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OPPORTUNITIES AND CONSTRAINTS FOR
MEDIUM-SCALE ORGANIC WASTE
TREATMENT WITH FLY LARVAE
COMPOSTING
S. DIENER*, C. LALANDER**, C. ZURBRUEGG*, B. VINNERÅS**
*Eawag: Swiss Federal Institute of Aquatic Science and Technology, Sandec:
Department of Water and Sanitation in Developing Countries, Ueberlandstrasse
133, 8600 Duebendorf, Switzerland
** Department of Energy and Technology, Swedish University of Agricultural
Sciences, Box 7032, 75007 Uppsala, Sweden
SUMMARY: The use of the black solider fly, Hermetia illucens, for conversion of organic waste
streams into valuable animal protein has become a hot topic in the past decade. Large-scale
protein production facilities treating up to 200 tonnes of waste per day are already in operation,
with focus on protein production. On the other end of the spectrum are decentralised small-scale
household composting systems focusing on waste treatment, motivated by the thought of self-
sufficiency. In the middle of the scale – waste management systems treating up to 10 tonnes per
day – there is of yet no alternative. There are benefits and constrains, with both large- and small-
scale BSF treatment. However, by combining the advantages of the centralised large-scale
protein production systems with the benefits of decentralised waste management strategies,
many of the constraints can be overcome. In this paper is suggested a semi-centralised BSF-
treatment approach that could bridge the lack of waste management in places current
management strategies have failed. The absence of adequate organic waste management has dire
health implications in low and middle-income countries and serious negative impacts on the
environment all around the world. In semi-centralised BSF treatment, a centralised facility is
used for fly rearing – for the production of small larvae required for the treatment – and for the
refinery of the products generated from the treatment (grown larvae and residue). From the
centralised BSF Rearing and Refinery (BSF R2) facility, small larvae are sent to decentralised
waste treatment units located at the place of waste production. The great volume reduction
occurring in the treatment (80-85% on a wet weight basis) greatly reduce the need for
transportation, while the valuable products generated from the treatment (animal protein and
organic fertiliser) renders the treatment an economically viable option for the clients using the
treatment units, while also allowing for business opportunities for waste management
entrepreneurs operating a BSF R2 facility. The flexibility in waste source and amounts possible
to treat with BSF-technology, along with the refining of high-value products and the reduced
need for transportation, can make the semi-centralised BSF-treatment approach a key player in
providing organic waste treatment in areas that today are either completely lacking any service
or that are not adequately treating the organic fraction. This would substantially improve the
health of millions and considerably reduce the negative environmental impacts associated with
poor organic waste management.

1. INTRODUCTION
Converting organic waste streams into insect protein and organic fertiliser with the larvae of
the black soldier fly, Hermetia illucens, has become a hot topic over the past decade (Makkar et
al., 2014; UNEP, 2010). Large scale treatment facilities, designed to treat up to 200 tonnes of
organic material per day have been built in places such as the Netherlands, Canada, South
Africa, China and USA. On the other end of the spectrum there is a vast number of households,
private chicken farmers and hobbyists operating black soldier fly (BSF) composting for personal
use (Olivier & Hyman, 2011). This leaves a gap in the market for medium-scale BSF treatment,
serving a local market. This is of great interest given the high share of organic material in the
waste streams – especially in low- and middle-income countries (LMIC) – and the growing
demand for locally produced animal feed. As such, BSF technology could provide an
opportunity for local entrepreneurs, serving not only the aforementioned demands but also
creating employment (Diener et al., 2011). The objective of this paper is to present a possible
business approach which combines the advantages of centralised protein production using BSF
with the benefits of decentralised waste management occurring at the neighbourhood or
household level.
2. THE BLACK SOLDIER FLY TECHNOLOGY
Larvae of the black soldier fly feed on decaying organic matter. In nature this can range from
rotting fruits over manure and human faeces to carcasses (Booram et al., 1977; Bradley, 1930;
Dunn, 1916; Jirón & Solano, 1988). Their voracity can thus be harnessed to convert the organic
fraction of waste into larval biomass. Larvae, provided a suitable feed source and adequate
temperature, develop into the final larval stage (prepupae) within two to three weeks. They
consist of ~35% protein and ~30% crude fat (Diener et al., 2009; Li et al., 2011; Zhou et al.,
2013). In the process, the waste is reduced 60-80% and turned into larval biomass at a waste-to-
biomass conversion rate of 20% based on dry matter (Diener et al., 2011; Dortmans, 2015). With
constantly increasing prices for fishmeal (index mundi, 2015) – today the most common protein
of animal origin in animal feed – the production of insect meal has a great potential for
entrepreneurs. In particular the fairly young black soldier fly technology underwent a significant
innovative boost since the turn of the millennium. About a dozen companies have already
started, or are about to start, protein production with BSF and are stating a material input
capacity of 200 to 1,000 tons per day. Large-scale facilities focus on protein production rather
than on waste management. Homogenous and pure input materials such as brewery waste, pre-
consumer food waste, chicken manure, and slaughterhouse waste allow for a controllable and
stable production of high value animal protein. However, competition with biogas or composting
plants can have a negative influence on the availability and thus the price of these resources. The
other extreme of the spectrum regarding the scale is the great variety of household based BSF-
treatment reactors mostly developed and promoted by enthusiastic hobbyists. Designs and gained
experiences are being spread through blogs and discussion forums on the internet. A wide range
of designs of great creativity can be found online (example: http://blacksoldierflyblog.com/). The
motivation often comes from the thought of self-sufficiency: the desire of treating one’s own
waste, while producing chicken or fish feed for one’s own animals. Although most of the
individual experiences published on the internet origin from northern countries, the on-site
technologies using BSF are often brought up as a low-tech and low-cost solution when
discussing organic waste management in LMIC where municipal solid waste (MSW) consists up
to 80% of organic material (UN-HABITAT, 2010).

3. SOLID WASTE MANAGEMENT
The challenges concerning organic waste handling differ somewhat between LMIC and high-
income countries (HIC), however, similar solutions can still be applied. The difficulties in
providing an accurate level of public waste management service in the urban centres in LMICs
are often attributed to the poor financial status of the managing municipal corporations (Sharholy
et al., 2008). The question is: why are cities in LMIC not drowning in solid waste even when
public services fail? The informal sector takes a great share of the waste management by
diverting valuables from the waste stream, bringing it back in circulation. In Delhi, 150,000
waste pickers divert 25% of the total solid waste (UN-HABITAT, 2010) and in a selected urban
area belonging to Mexico City with 1.7 million inhabitants, the informal waste sector not only
generates an income of USD 12 million per year but also save the municipality USD 2.6 million
for collection services (Medina, 2005). The informal waste business is flourishing but recovery
of waste is limited to sellable recyclables such as glass, metal, paper and plastics. The organic
fraction is still not being recycled, but rather discharged in landfills or in more or less illegal
dumps (Komakech et al., 2014), creating an olfactory nuisance that poses a serious health risk. In
HIC the solid waste is collected to a great extend (>76%); albeit the degree and selection of
treatment differ greatly between countries. The solid waste comprise on average to 28% of
organic material in HIC; 70% of the solid waste is landfilled in Australia, 26% in Norway and
66% in Ireland, while nearly no solid waste is landfilled in Japan, Sweden and Switzerland
(Hoornweg & Bhada-Tata, 2012). The organic waste fraction comprise of food-, garden- and
market waste, and also to a greater or lesser extend different animal manures (Asomani-Boateng
& Haight, 1999). Animal manures are a source of pathogenic bacteria, virus and parasites (Pell,
1997), while rodents and flies, known vectors of disease transmission, are attracted to rotting
food and manures. In conjunction to the health risk associated with inadequate organic waste
management, major environmental issues can be expected: an increased green-house gas
emissions from partially anaerobic decomposition of organic material (UNEP, 2010) and
eutrophication of water bodies as the nutrients contained in the organic fraction leach out
(Sharpley et al., 1994). The health related impacts are greater in LMIC, where a great proportion
of the organic fraction of the waste is discharged untreated in urban environment where many
people move around (Komakech et al., 2014), while the negative environmental impacts are of
great concern in LMIC as well as in HIC (Hoornweg & Bhada-Tata, 2012).
With a technology at hand which turns the organic fraction of municipal solid waste into
valuable products, its collection will become more attractive. Precondition will be, just as it is
with other recyclables, a reliable purchaser and an attractive price. However, unlike plastic or
paper, organic waste cannot be stored until a large bulk for shipping has accumulated or until the
reselling price is right. The putridness of the material along with the risk of disease transmission
requires prompt processing and treatment. The collected waste needs thus either to be treated on
spot or has to be moved to the centralised treatment site daily.
Decentralised municipal organic waste treatment using BSF thus have the potential to
incentivise collection and treatment of municipal organic waste, which could contribute to
improved health-related quality of life in LMIC, and greatly reduce the negative environmental
impact of poor organic waste management.
Five key attributes make BSF-technology an attractive treatment option for organic waste:
I) A waste reduction up to 80% on wet weight basis have been demonstrated (Dortmans,
2015). If applied locally, costs for waste transport and space requirements for landfills can thus
be reduced drastically. It could furthermore reduce the risk for open dumps that often appear in
LMIC. While the material is reduced, most nutrients contained in the organic waste (apart from
nitrogen that is partially evaporated) remain in the residues, which can be seen as a concentrated
organic fertiliser, simplifying the recycling of plant nutrients from the organic waste back to

arable land (Lalander et al., 2015).
II) At the same time the biomass is being converted into high quality animal protein, an
important resource for local chicken and fish farmers. In Kampala, Uganda, for example,
chicken farmers, as result of limited trust in the feed industry and the quality of their products,
buy small dried fish on the market and, after grinding, mix it together with grains to produce
their own feed (Diener et al., 2014).
III) A high waste-to-biomass conversion rate of up to 23% on wet weight basis (Banks et al.,
2014) has been demonstrated, which would results in a satisfactory output quantity even for
medium waste quantities.
IV) The technology has been proved to inactivate zoonotic bacteria such as Salmonella spp.
(Lalander et al., 2013). That means that the risk of disease transmission between animals and
between animals and humans is reduced if using this technology on farm level or when treating
waste of animal origin in general (e.g. chicken manure or slaughterhouse waste).
V) As from a socio-economic point of view, given a suitable waste collection scheme, the
locally operated BSF treatment facility could act as a collection point for the informal waste
collection sector. Similar to middle men of plastic or glass recycling, the operator of a BSF
treatment facility may buy organic waste from either waste pickers or from farmers, thus
generating an income while at the same time reducing negative environmental impact of
inadequate organic waste and manure management (UN-HABITAT, 2010).
4. COMBINING THE PROTEIN BUSINESS WITH WASTE MANAGEMENT
Besides their beneficial aspects, both, the BSF-driven centralised large-scale protein
production and the decentralised waste treatment BSF-technologies are facing obstacles when it
comes to handling organic waste (Table 1).
Table 1: Large-scale BSF production versus on-site BSF treatment systems
Centralised BSF production:
Industrial scale, processing several tons of homogenous waste per day with focus on protein production.
Advantages
Disadvantages
• Homogeneous waste source guarantees steady
operational conditions
• Economy of scale
• Specialised in-house know how
• Big quantities of products allows supply contracts
with animal feed industry
• Professional quality control
• Emissions can be centrally controlled
• Competition for pure waste sources with other
processes (e.g. biogas) increases price for the raw
material
• Large investment needed
• Conveyance of large quantities results in high
transportation costs
• Little flexibility to adapt the process if waste
source or market changes.
Decentralised stand-alone waste treatment with BSF:
Household or neighbourhood facilities, processing up to 100 kilograms of mixed waste per day with focus on
waste treatment.
Advantages
Disadvantages
• Waste is for free
• Waste can be treated where it is produced
• Allowing for waste treatment in areas hard to access
(urban slum areas, rural farms)
• Short transport ways for bulky material
• Can react to demographic change with multiplication
• Technology and operational procedures adapt to the
local context (waste characteristics, market for
products)
• Requires waste segregation at source and/or sorting
before treatment
• Low degree of efficiency or even risk of system
failure due to unskilled personnel
• No established and guaranteed market for products
• Little product quality control
• Little control over hygiene standards

A business model which combines the advantages of the industrial BSF systems with the
flexibility and waste treatment potential of the decentralised BSF facilities could contribute both
to local economic growth and wide-ranging organic waste management.
A segregation of tasks seems promising: operation of a centralised BSF Rearing and Refinery
(BSF R2) facility serving a number of decentralised, robust treatment units may facilitate the
uptake of the BSF waste treatment technology (Figure 1). The critical processes, where skilled
labour and specialised equipment is needed, are located at the BSF R2 facility. The treatment of
the waste happens where the material is generated, e.g. at a poultry or pig farm, or in a LMIC
perspective, at a collection point where waste pickers deposit their pickings and get paid.
Treatment devices, each capable of treating 200-1,000 kg per day, are dispersed over an area
which is reachable by a courier within a reasonable time. The courier delivers the young larvae
required for the treatment and in return collects the products of the treatment process (grown
larvae and residue). The products are post-processed and prepared for sale at the BSF R2.
Figure 1: Centralised BSF Rearing and Refinery facility with outsourced treatment units
The process requires a high number of young fly larvae to be added to the system and a well-
operated rearing facility is therefore key for a well-functioning BSF-system. Thanks to the scale
of the centralised facility, the fly colony can be operated by skilled workers who react on sudden
fly population fluctuations or outbreaks of diseases. Another advantage of the combined facility
is that the degree of capacity utilisation for the equipment for sanitisation, refining and
packaging of the products is much higher. The investment will thus amortise faster. Furthermore,
with the refinery processes happening under the same roof, quality control can be ensured much
easier following standard protocols and using calibrated checking devices.
The treatment itself is a predictable, hands-on process. Given the right conditions, larvae will

feed on the waste and can be collected after they have done the job. However, there is a risk of
system collapse if the treatment units are not operated adequately. To prevent this, the treatment
devices have to be without frills, robust and have to come with clear and simple instructions for
operation and maintenance.
5. DIFFERENT SCENARIOS FOR THE TREATMENT
The treatment can be located wherever a client accumulates waste on a regular basis; be it a
chicken farmer, a restaurant or a small entrepreneur who collects organic waste for this purpose
alone. By outsourcing the treatment, a great share of the transport costs can be cut. Material
treated with larvae of the black soldier fly is being reduced by up to 80% on wet weight basis:
1,000 kg of organic material is thus converted into 200 kg of residue and 200 kg of larval
biomass; transportation can thus be reduced by 60%.
There are several possible scenarios regarding ownership of the treatment device(s) and who
is responsible for operation, maintenance and harvest. Depending on the skills and needs of a
client, the treatment device can be bought or hired from the company who runs the BSF R2
facility. Operation should be up to the client itself but certain maintenance tasks could be part of
a service contract. The quality and quantity depends on the input waste material, but also on the
operation of the treatment unit. A purchase commitment for the products should thus be linked to
a certain minimum quality requirement.
Establishing a semi-centralised BSF treatment operation requires:
 development of a robust treatment unit which withstands mal-operation and which can
cope with extreme environmental conditions (i.e. temperature and moisture);
 build-up of a healthy fly colony, able to generate sufficient larvae on a regular basis;
 develop and evaluate different business models for context-specific optimisation of semi-
centralised BSF treatment;
 assessment of different logistics models for larvae distribution and product collection to
identify the limiting factors.
However, successful projects need to be flexible in design, adaptable and operational in ways
that best meet current social, economic and environmental conditions, which are also likely to
change over time and vary depending on the geographic area of the project (Zurbrügg et al.,
2012).
6. FINAL REMARKS
With the conversion of organic waste into valuable products, the flexible scalability and the
reduced need for transportation; semi-centralised BSF-technology has the potential to play a key
role in improving the health conditions of many in LMIC and reducing the negative
environmental impact of inadequate or insufficient organic waste management in LMIC as well
as HIC. Due to the great plasticity in source and amounts of waste possible to treat, the BSF-
technology can serve and benefit a public toilet entrepreneur in a bustling urban centre of an
African city, a medium-scale pig-producer operating in a rural area of North America and an
organic waste manager in an Asian food market.

ACKNOWLEDGEMENT
The work presented here was realised within the Eco-Innovera program SPROUT¸ funded by
BAFU (Switzerland), FORMAS (Sweden) and Pacovis AG.
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